Commentary: Australian Case Rekindles Debate on AI in Thoroughbreds

Pedigree analyst Avalyn Hunter discusses the debate over artificial insemination use in Thoroughbreds.

The debate over whether to permit artificial insemination (AI) in the Thoroughbred has been around just about as long as the practice, which was first studied seriously in the late 1800s as an alternate to natural breeding. To date, all major Thoroughbred registries ban foals conceived by AI, along with those produced by embryo transfer and other assisted reproduction techniques.

The latest challenge, a suit filed in Australia by owner-breeder Bruce McHugh on the grounds that the requirement for natural service constituted an unlawful restraint of trade, was denied in a Dec. 19 court decision rendered by Justice Alan Robertson. Had the ruling gone otherwise, Thoroughbred regulatory bodies around the world now would be faced with the issue of whether to open their own registries and racing to AI-sired animals or to ban Australian horses so begotten--no light consideration, given that Australia is the second largest Thoroughbred breeding market behind the United States.

Many arguments have been advanced for and against AI based on considerations such as safety, boarding expenses, the potential for spread of diseases and genetic disorders, and potential effects on stud fees. But from a pedigree perspective, the main argument boils down to genetic diversity. And even there, opinions are mixed.

On the "pro" side, access to AI potentially could permit mare owners to make use of a much wider choice of stallions. The greatest beneficiaries would be breeders in the smaller regional markets and possibly in California, where the distances between clusters of breeding farms in the northern and southern parts of the state effectively divide the state into smaller sub-regions. Provided that reliable same-day or next-day courier service is available, chilled semen can be shipped from virtually anywhere at much less expense than shipping a mare to a breeding farm hundreds or even thousands of miles away; frozen semen is also available. For those breeders willing to take the time and effort to study the conformation and pedigree of their mares carefully and choose the stallions that best suit them regardless of fashion, AI presents a widening of opportunities.

Those opportunities would not be limitless, however. Some stallions' semen simply does not tolerate chilling or freezing well; for those animals, natural cover or on-site insemination of mares would remain the only viable options. Further, AI works best when handled by an experienced veterinarian--especially when mares with irregular cycles or declining fertility are involved--and veterinary clinics with the needed expertise in equine reproductive techniques tend to be clustered in the same areas where the majority of the nation's breeding stock now reside.

The greatest argument on the "con" side is the potential for a small number of popular sires to so dominate the breeding market that few new sires would even be given a chance. Even the most fertile and vigorous of stallions would be hard put to impregnate 200 mares by natural cover during a normal breeding season, but the same single ejaculation that can impregnate one mare by natural cover can potentially impregnate 10 or more mares by AI. With AI permitted, the manager of a popular stallion conceivably could slash the stud fee charged and still make higher profits by selling AI "seasons" to as many mares as possible. Legal experts already have opined that attempts to restrain such traffic by regulations allowing only so many foals per stallion to be registered annually would not survive a court challenge.

In the short term, the chance to make a quick windfall profit probably would have exactly the results feared; this phenomenon already has been observed in the Quarter Horse and the Standardbred. But over a longer period of time, the law of supply and demand appears to provide its own controls. The Standardbred is an example: After an initial period in which stallion books of in-demand stallions rose to new heights following the introduction of AI, the overabundance of youngsters sired by those same sires dropped prices in the auction ring for all but the most outstanding specimens. In order to protect the value of their "product," most major stallion owners ended up voluntarily dropping back book sizes to more realistic levels.

While huge books probably would be subject to the same rapid expansion-glut-pruning cycle that has been observed following many other changes in business paradigms, one danger of the "expansion" phase of the cycle is that a deleterious recessive gene might be spread further and wider than would otherwise be the case should one be present in the genome of a highly popular sire. Such a phenomenon already has been observed in the Quarter Horse, though it is not clear how much the breed's AI policies contributed to the spread of hereditary equine regional dermal asthenia (HERDA), a recessive disorder affecting the strength of the skin and other connective tissues that can be traced back to a single stallion (Poco Bueno) and his immediate ancestors. But the other side of the coin is that beneficial traits also could be built up rapidly in the population by greater use of truly superior animals; as cattle breeders have been fond of saying, "the bull is half the herd."

For now, AI remains off the table as an option in the Thoroughbred industry. But whether or not McHugh chooses to appeal, further court challenges are sure to come. Should AI ever become legal, the Thoroughbred will doubtless survive; in some breeders' hands, it could even thrive anew. But it will be, at best, a mixed blessing and subject to the law of unexpected consequences--surely reason enough to make haste slowly.

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